I've got a lot of books in Russian and Bulgarian, in .mobi format - will they work right out of the box on the K4NT or will I have to use workarounds (and if so, what kind?) to read them on it?

Also I've read that the basic K4's battery holds for up to a month when you read up 30 minutes per day. Since I don't really trust battery times by the manufacturers, maybe you guys can tell me how it compares to say the Gen3 or PRS505 in terms of page turns?